bilinear
collinear
lengthways
lengthwise
lineal
linelike
rectilineal
rectilinear
simple
unsubdivided
Plimsoll line
Plimsoll mark
arrowlike
catenary
consecutive
dead straight
direct
even
flat
high-water mark
horizontal
in a line
level
load waterline
narrow
ordinal
progressive
right
ruler-straight
sequent
sequential
serial
seriate
smooth
straight
straight-cut
straight-front
straight-side
streamlined
successional
successive
tidemark
true
unbending
unbent
unbowed
unbroken
uncurved
undeflected
undeviating
undistorted
uninterrupted
unswerving
unturned
upright
vertical
interlineal
interlinear
correspond
digital
geometric
magnetic
mathematical
molecular
precise
spatial
structural
skinnier
holistic